So I hit for 2 hours last night with my Ki5 strung with Luxilon Fluoro 17 strung at 50lbs. I think this racquet/string combo is my new holy grail! The power and control were amazing. My partner said he had never seen me play so well before.
Am I kidding myself? Maybe. I realize these strings are only supposed to last 3 hours, but I will know for sure after a week. I experienced zero arm pain today, and that's usually when I know if I screwed up my elbow or not.
Anyhow, very happy to report that a poly string seems to be working well with a Ki5.